The present invention relates to a device (a tool) for retrieving equipment which is stuck or broken in a borehole or the like. Within the art such arrangements are also called xe2x80x9cfishing toolsxe2x80x9d and are designed to take up so-called fish, that is to say severed, broken off, buckled drill strings plus coiled pipes, snubbing pipes, tapers from drill crowns and wires, and log tools, plugs, shafts and slick pipes and the like in offshore and onshore bore hole.
A tool for retrieving a drill string which is broken and stick in a well, is disclosed in Norwegian patent No. 177.361. The tool is fixed to a string and is lowered into the borehole to retrieve the drill string. The tool comprises a stationary grip part which is arranged enclosingly about part of the drill string, after which a central movable grip part of the tool is caused to be forced downward into the drill string for fixing it against the stationary grip part. The grip part is forced/moved downwards by detonating an explosive charge (on impact from a piston) so that the grip part is forced downward and into the drill string with a sufficient force to bring the string radially outwards to abut against the stationary grip part.
Also U.S. Pat. No. 4,580,826 discloses a pipe retrieval tool for retrieving a pipe which is stuck in a well. The tool includes a bell mouth for centering the pipe, and a spear is guided downwards into the pipe, and gripping devices carried by the spear, are released to engage the pipe so as to pull it to the surface. Reference is also made to U.S. Pat. No. 5,054,832.
The object of the present invention is to produce a novel construction of tools for retrieving of the different parts of objects which may be stuck or broken down within a bore hole or the like.
It is further an object to provide a novel design of such as a tool, i.,e.) the skirt of such a tool which is caused to enclose the equipment part (the fish) to be retrieved. Subsequently the equipment part is anchored to the skirt of the tool.
The device according to the invention is characterized in that the lower portion of the sleeve shaped movable grip part is partly cut away to form a part-cylindrical shape of a tongue or chisel design, and that the internal surface is similarly curved or is plane.
Preferred embodiments are defined in the independent patent claims 2-7.
By employment of both the skirt and the main piston including the different designs as defined according to the invention, all kinds of equipment (i.e. both pipe equipment, rods, log tools, partly flattened pipes which stick or is broken down within a bore hole or a well, easily may be wedged between the skirt of the tool and the main piston, and thereafter retrieved to the surface. The whole process may be carried out more readily than previously, such as by one run, in contrast to 2  less than  less than  runs greater than  greater than  minimum as have hitherto been usual.
Preferably the device is used in connection with a structure which fires the movable gripping part downward by detonation of an explosive charge, something which causes gripping part being fired downwards with very great force which is transferred radially outwards so that the equipment residue in a safe manner is squeezed/clamped to the external sleeve part. The hoisting of the equipment parts may thus occur with reduced risk of the parts loosen and falling down again. One is also ensured against unintentionally detonation of the explosive charge.
The tool consists of 4 main components and a number of lesser parts. The four parts are: main cylinder, skirt, inner cone together with main piston and firing pin. In addition come cutting pins, wedges, o-rings and primer ring and drive mix (explosive charge) with accessories.